The proposed work concerns the purification, biochemical characteristics, cellular localization and function of the two different acid phosphatases in bone and the enamel organ of molar tooth buds of suckling rat pups. Specific aims include: 1. To complete final purification, of the two bone acid phosphatases, E1 and E2, that have been purified 700- to 1000-fold, to verify the purity of the preparations, and to determine the characteristics of the enzymes. 2. To determine the reactive amounts of acid phosphatases in isolated bone cell populations. 3. To determine the localization of acid phosphatases by means of enzyme histochemistry and immunocytochemistry. 4. To determine the effects of parathyroid hormone and vitamin D on activity and tissue levels of acid phosphatases in bone and tooth buds.